Multi-mode electromechanical variable transmission

ABSTRACT

A vehicle includes a drive axle, a multi-mode transmission, and a controller coupled to the multi-mode transmission. The multi-mode transmission includes a first gear set having a first planetary gear carrier and a second gear set having a second planetary gear carrier, a first motor/generator coupled to the first gear set, a second motor/generator coupled to the second gear set and selectively coupled to a connecting shaft, a brake positioned to selectively limit a rotational movement of a ring gear of the second gear set when engaged, a first clutch selectively rotationally coupling the first gear set and the second gear set to the drive axle when engaged, and a second clutch selectively rotationally coupling the second motor/generator to the connecting shaft when engaged. The controller is configured to engage the brake and the clutches to selectively reconfigure the multi-mode transmission to an intermediate shift mode of operation.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application is a continuation of U.S. application Ser. No.15/601,670, filed May 22, 2017, which is a continuation of U.S.application Ser. No. 14/792,535, filed Jul. 6, 2015, now U.S. Pat. No.9,656,659, which is a continuation-in-part of U.S. application Ser. No.14/624,285, filed Feb. 17, 2015, now U.S. Pat. No. 9,651,120, all ofwhich are incorporated herein by reference in their entireties.

BACKGROUND

Internal combustion engine vehicles, hybrid vehicles, and electricvehicles, among other types of vehicles, include transmissions.Traditional vehicle transmissions use gears and gear trains to providespeed and torque conversions from a rotating power source (e.g., anengine, a motor, etc.) to another device (e.g., a drive shaft, wheels ofa vehicle, etc.). Transmissions include multiple gear ratios selectivelycoupled to the rotating power source with a mechanism that may alsoselectively couple an output to the various gear ratios.

SUMMARY

One exemplary embodiment relates to a vehicle that includes a driveaxle, a multi-mode transmission, and a controller coupled to themulti-mode transmission. The multi-mode transmission includes a firstgear set having a first planetary gear carrier and a second gear sethaving a second planetary gear carrier, a first motor/generator coupledto the first gear set, a second motor/generator coupled to the secondgear set and selectively coupled to a connecting shaft, a brakepositioned to selectively limit a rotational movement of a ring gear ofthe second gear set when engaged, a first clutch selectivelyrotationally coupling the first gear set and the second gear set to thedrive axle when engaged, and a second clutch selectively rotationallycoupling the second motor/generator to the connecting shaft whenengaged. The controller is configured to engage the second clutch, thebrake, and the first clutch to selectively reconfigure the multi-modetransmission to an intermediate shift mode of operation.

Another exemplary embodiment relates to a drive system for a vehiclethat includes a first gear set having a first sun gear, a first ringgear, a first plurality of planetary gears coupling the first sun gearto the first ring gear, and a first carrier rotationally supporting thefirst plurality of planetary gears, a second gear set having a secondsun gear, a second ring gear, a second plurality of planetary gearscoupling the second sun gear to the second ring gear, and a secondcarrier rotationally supporting the second plurality of planetary gears,a first electrical machine coupled to the first gear set, a secondelectrical machine coupled to the second gear set, a connecting shaftcoupled to the first gear set, a brake positioned to selectively limit arotational movement of the second gear set when engaged, a first clutchselectively rotationally coupling the first carrier and the secondcarrier to a driveshaft output of the vehicle when engaged, and a secondclutch selectively rotationally coupling the second electrical machineto the connecting shaft when engaged. The drive system is selectivelyreconfigurable into an intermediate shift mode of operation, in whichthe brake, the first clutch, and the second clutch are engaged.

Another exemplary embodiment relates to a method of operating amulti-mode transmission of a vehicle. The method includes engaging abrake and first clutch of the multi-mode transmission to configure themulti-mode transmission into a first mode of operation whereby a firstelectromagnetic device is coupled to a connecting shaft, the firstclutch coupling a pair of carriers of a first planetary gear set and asecond planetary gear set to a driveshaft output of the vehicle whenengaged, engaging a second clutch of the multi-mode transmission tocouple the connecting shaft and a second electromagnetic device, therebyconfiguring the multi-mode transmission into an intermediate shift mode,and at least one of (i) disengaging the brake to complete areconfiguration of the multi-mode transmission into a second mode ofoperation and (ii) disengaging the second clutch to revert themulti-mode transmission into the first mode of operation from theintermediate shift mode.

The invention is capable of other embodiments and of being carried outin various ways. Alternative exemplary embodiments relate to otherfeatures and combinations of features as may be recited herein.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure will become more fully understood from the followingdetailed description, taken in conjunction with the accompanyingfigures, wherein like reference numerals refer to like elements, inwhich:

FIG. 1 is a schematic view of a drive train for a vehicle, according toan exemplary embodiment;

FIG. 2 is a detailed schematic view of the drive train of FIG. 1,according to an exemplary embodiment;

FIG. 3 is a schematic diagram of a control system for the drive train ofFIG. 1, according to an exemplary embodiment.

FIG. 4 is a detailed schematic view of a drive train configured in astartup mode of operation, according to an exemplary embodiment;

FIG. 5 is a detailed schematic view of a drive train configured in a lowrange mode of operation, according to an exemplary embodiment;

FIG. 6 is a detailed schematic view of a drive train configured in a midrange mode of operation, according to an exemplary embodiment;

FIG. 7 is a detailed schematic view of a drive train configured in ahigh range mode of operation, according to an exemplary embodiment;

FIG. 8 is a detailed schematic view of a drive train configured in anintermediate shift mode of operation, according to an exemplaryembodiment;

FIG. 9 is a detailed schematic view of a drive train configured in a lowspeed reverse mode of operation, according to an exemplary embodiment;and

FIG. 10 is a detailed schematic view of a drive train configured in ahigh speed reverse mode of operation, according to an exemplaryembodiment.

DETAILED DESCRIPTION

Before turning to the figures, which illustrate the exemplaryembodiments in detail, it should be understood that the presentapplication is not limited to the details or methodology set forth inthe description or illustrated in the figures. It should also beunderstood that the terminology is for the purpose of description onlyand should not be regarded as limiting.

According to an exemplary embodiment, a multi-mode electromechanicalvariable transmission is provided as part of a vehicle and isselectively reconfigurable into one of a plurality of operating modes.The vehicle may also include an engine, a first electromagnetic device,and second electromagnetic device. In one embodiment, at least one ofthe first electromagnetic device and the second electromagnetic deviceprovides rotational mechanical energy to start the engine. In anotherembodiment, the engine provides a rotational mechanical energy input toboth the first and second electromagnetic devices such that eachoperates as a generator to generate electrical energy. In still otherembodiments, one of the first electromagnetic device and the secondelectromagnetic device are configured to receive a rotational mechanicalenergy output from at least one of the engine and the multi-modeelectromechanical variable transmission and provide an electrical energyoutput to power a control system and/or the other electromagneticdevice.

According to the exemplary embodiment shown in FIGS. 1-2, a vehicle 10includes an engine 20 coupled to a transmission, shown as transmission30. In one embodiment, engine 20 is configured to combust fuel andprovide a mechanical energy input to transmission 30. By way of example,engine 20 may be configured to provide a rotational mechanical energyinput to transmission 30. As shown in FIGS. 1-2, a first electricalmachine, electromagnetic device and/or motor/generator, shown as firstelectromagnetic device 40, and a second electrical machine,electromagnetic device and/or motor/generator, shown as secondelectromagnetic device 50, are coupled to transmission 30.

Referring again to the exemplary embodiment shown in FIG. 1, vehicle 10includes a front axle, shown as front axle 60, and a rear axle, shown asrear axle 70. As shown in FIG. 1, front axle 60 includes a pair oftractive elements, shown as tires 62, coupled to a front differential,shown as front differential 64. Rear axle 70 includes a pair of tractiveelements, shown as tires 72, coupled to a rear differential, shown asrear differential 74, according to an exemplary embodiment. According tothe exemplary embodiment shown in FIG. 1, front differential 64 iscoupled to transmission 30 with a front axle driveshaft 66 and reardifferential 74 is coupled to transmission 30 with a rear axledriveshaft 76. While shown as coupled to tires 62 and tires 72, frontdifferential 64 and rear differential 74 may be coupled to various othertypes of tractive elements (e.g., tracks, etc.), according toalternative embodiments. As shown in FIG. 1, front axle driveshaft 66and rear axle driveshaft 76 are configured to transport power from firstelectromagnetic device 40, second electromagnetic device 50, and engine20 to tires 62 and tires 72, respectively. Vehicle 10 may include aplurality of front differentials 64 that may be coupled or a pluralityof rear differentials 74 that may be coupled, according to variousalternative embodiments.

Engine 20 may be any source of rotational mechanical energy that isderived from a stored energy source. The stored energy source isdisposed onboard vehicle 10, according to an exemplary embodiment. Thestored energy source may include a liquid fuel or a gaseous fuel, amongother alternatives. In one embodiment, engine 20 includes an internalcombustion engine configured to be powered by at least one of gasoline,natural gas, and diesel fuel. According to various alternativeembodiments, engine 20 includes at least one of a turbine, a fuel cell,an electric motor or still another device. According to one exemplaryembodiment, engine 20 includes a twelve liter diesel engine capable ofproviding between approximately 400 horsepower and approximately 600horsepower and between approximately 400 foot pounds of torque andapproximately 2000 foot pounds of torque. In one embodiment, engine 20has a rotational speed (e.g., a rotational operational range, etc.) ofbetween 0 and 2,100 revolutions per minute. Engine 20 may be operated ata relatively constant speed (e.g., 1,600 revolutions per minute, etc.).In one embodiment, the relatively constant speed is selected based on anoperating condition of engine 20 (e.g., an operating speed relating to apoint of increased fuel efficiency, etc.).

In one embodiment, at least one of first electromagnetic device 40 andsecond electromagnetic device 50 provide a mechanical energy input totransmission 30. By way of example, at least one of firstelectromagnetic device 40 and second electromagnetic device 50 may beconfigured to provide a rotational mechanical energy input totransmission 30 (i.e., at least one of first electromagnetic device 40and second electromagnetic device 50 may operate as a motor, etc.). Atleast one of first electromagnetic device 40 and second electromagneticdevice 50 may receive a mechanical energy output from at least one ofengine 20 and transmission 30. By way of example, at least one of firstelectromagnetic device 40 and second electromagnetic device 50 may beconfigured to receive a rotational mechanical energy output from atleast one of engine 20 and transmission 30 and provide an electricalenergy output (i.e., at least one of first electromagnetic device 40 andsecond electromagnetic device 50 may operate as a generator, etc.).According to an exemplary embodiment, first electromagnetic device 40and second electromagnetic device 50 are capable of both providingmechanical energy and converting a mechanical energy input into anelectrical energy output (i.e., operate as a motor and a generator,etc.). The operational condition of first electromagnetic device 40 andsecond electromagnetic device 50 (e.g., as a motor, as a generator,etc.) may vary based on a mode of operation associated with transmission30.

According to the exemplary embodiment shown in FIG. 2, a drive systemfor a vehicle, shown as drive system 100, includes engine 20,transmission 30, first electromagnetic device 40, second electromagneticdevice 50, front axle driveshaft 66, and rear axle driveshaft 76. Asshown in FIG. 2, transmission 30 includes a first gear set, shown aspower split planetary 110, and a second gear set, shown as outputplanetary 120. In one embodiment, power split planetary 110 and outputplanetary 120 are disposed between first electromagnetic device 40 andsecond electromagnetic device 50. In an alternative embodiment, one orboth of power split planetary 110 and output planetary 120 arepositioned outside of (i.e., not between, etc.) first electromagneticdevice 40 and second electromagnetic device 50. As shown in FIG. 2,power split planetary 110 is directly coupled to engine 20.

Referring to the exemplary embodiment shown in FIG. 2, power splitplanetary 110 is a planetary gear set that includes a sun gear 112, aring gear 114, and a plurality of planetary gears 116. The plurality ofplanetary gears 116 couple sun gear 112 to ring gear 114, according toan exemplary embodiment. As shown in FIG. 2, a carrier 118 rotationallysupports the plurality of planetary gears 116. In one embodiment, firstelectromagnetic device 40 is directly coupled to sun gear 112 such thatpower split planetary 110 is coupled to first electromagnetic device 40.By way of example, first electromagnetic device 40 may include a shaft(e.g., a first shaft, an input shaft, an output shaft, etc.) directlycoupled to sun gear 112.

Referring still to the exemplary embodiment shown in FIG. 2, outputplanetary 120 is a planetary gear set that includes a sun gear 122, aring gear 124, and a plurality of planetary gears 126. The plurality ofplanetary gears 126 couple sun gear 122 to ring gear 124, according toan exemplary embodiment. As shown in FIG. 2, a carrier 128 rotationallysupports the plurality of planetary gears 126. In one embodiment, secondelectromagnetic device 50 is directly coupled to sun gear 122 such thatoutput planetary 120 is coupled to second electromagnetic device 50. Byway of example, second electromagnetic device 50 may include a shaft(e.g., a second shaft, an input shaft, an output shaft, etc.) directlycoupled to sun gear 122. Carrier 118 is directly coupled to carrier 128,thereby coupling power split planetary 110 to output planetary 120,according to the exemplary embodiment shown in FIG. 2. In oneembodiment, directly coupling carrier 118 to carrier 128 synchronizesrotational speeds of carrier 118 and carrier 128.

According to an exemplary embodiment, transmission 30 includes a firstclutch, shown as power split coupled clutch 130. In one embodiment,power split coupled clutch 130 is positioned downstream of power splitplanetary 110 (e.g., between power split planetary 110 and front axledriveshaft 66 or rear axle driveshaft 76, etc.). In an alternativeembodiment, power split coupled clutch 130 is directly coupled to engine20. As shown in FIG. 2, power split coupled clutch 130 is positioned toselectively couple power split planetary 110 and output planetary 120with a shaft, shown as output shaft 32. In one embodiment, power splitcoupled clutch 130 allows a vehicle to be towed without spinning thegears within transmission 30 (e.g., power split planetary 110, outputplanetary 120, etc.). Output shaft 32 may be coupled to rear axledriveshaft 76 and selectively coupled to front axle driveshaft with adeclutch assembly, shown as front declutch collar shift 34. Frontdeclutch collar shift 34 may be engaged and disengaged to selectivelycouple front axle driveshaft 66 to output shaft 32 of transmission 30(e.g., to facilitate operation of a vehicle in a rear-wheel-drive-onlymode, an all-wheel-drive mode, a four-wheel-drive mode, etc.).

As shown in FIG. 2, transmission 30 includes a second clutch, shown asinput coupled clutch 140. Input coupled clutch 140 is positioned toselectively couple second electromagnetic device 50 with engine 20,according to an exemplary embodiment. Input coupled clutch 140 maythereby selectively couple engine 20 to output planetary 120. As shownin FIG. 2, transmission 30 includes a shaft, shown as connecting shaft36. According to an exemplary embodiment, connecting shaft 36 extendsfrom engine 20, through second electromagnetic device 50, and throughoutput planetary 120 to power split planetary 110. Connecting shaft 36couples engine 20 with power split planetary 110, according to theexemplary embodiment shown in FIG. 2. In one embodiment, connectingshaft 36 directly couples engine 20 with ring gear 114 of power splitplanetary 110. Input coupled clutch 140 may selectively couple secondelectromagnetic device 50 with connecting shaft 36. According to anexemplary embodiment, the shaft (e.g., input/output shaft, etc.) offirst electromagnetic device 40 and the shaft (e.g., input/output shaft,etc.) of second electromagnetic device 50 are radially aligned withpower split planetary 110, output planetary 120, and connecting shaft 36(e.g., centerlines thereof are aligned, etc.). As shown in FIG. 2,transmission 30 includes a third clutch, shown as output coupled clutch150. Output coupled clutch 150 is positioned to selectively coupleoutput planetary 120 with output shaft 32, according to an exemplaryembodiment. In one embodiment, output shaft 32 is radially offset frompower split planetary 110, output planetary 120, and connecting shaft 36(e.g., radially offset from centerlines thereof, etc.).

Referring again to the exemplary embodiment shown in FIG. 2,transmission 30 includes brake, shown as output brake 170. Output brake170 is positioned to selectively inhibit the movement of at least aportion of output planetary 120 (e.g., ring gear 124, etc.), accordingto an exemplary embodiment. In one embodiment, output brake 170 isbiased into an engaged position (e.g., with a spring, etc.) andselectively disengaged (e.g., with application of pressurized hydraulicfluid, etc.). In other embodiments, output brake 170 ishydraulically-biased and spring released. In still other embodiments,the components of transmission 30 are still otherwise engaged anddisengaged (e.g., pneumatically, etc.). By way of example, output brake170 and output coupled clutch 150 may be engaged simultaneously tofunction as a driveline brake (e.g., a braking mechanism to slow down avehicle, etc.).

As shown in FIG. 2, transmission 30 includes a gear set 180 that couplescarrier 118 and carrier 128 to output shaft 32. In one embodiment, gearset 180 includes a first gear, shown as gear 182, in meshing engagementwith a second gear, shown as gear 184. As shown in FIG. 2, gear 182 isrotatably coupled to carrier 118 and carrier 128. By way of example,gear 182 may be fixed to a component (e.g., shaft, tube, etc.) thatcouples carrier 118 and carrier 128. As shown in FIG. 2, power splitcoupled clutch 130 is positioned to selectively couple gear 184 withoutput shaft 32 when engaged. With power split coupled clutch 130disengaged, relative movement (e.g., rotation, etc.) may occur betweengear 184 and output shaft 32.

According to an exemplary embodiment, transmission 30 includes a gearset, shown as gear set 190, that couples output planetary 120 to outputshaft 32. As shown in FIG. 2, gear set 190 includes a first gear, shownas gear 192, coupled to ring gear 124 of output planetary 120. Gear 192is in meshing engagement with a second gear, shown as gear 194,according to an exemplary embodiment. As shown in FIG. 2, gear 194 iscoupled to a third gear, shown as gear 196. In other embodiments, gear192 is directly coupled with gear 196. By way of example, gear set 190may not include gear 194, and gear 192 may be directly coupled to (e.g.,in meshing engagement with, etc.) gear 196. As shown in FIG. 2, outputcoupled clutch 150 is positioned to selectively couple gear 196 withoutput shaft 32 when engaged. With output coupled clutch 150 disengaged,relative movement (e.g., rotation, etc.) may occur between gear 196 andoutput shaft 32. By way of example, output coupled clutch 150 may beengaged to couple ring gear 124 to output shaft 32. Output brake 170 ispositioned to selectively limit the movement of gear 192 when engaged tothereby also limit the movement of ring gear 124, gear 194, and gear196.

According to the exemplary embodiment shown in FIG. 3, a control system200 for a vehicle includes a controller 210. In one embodiment,controller 210 is configured to selectively engage, selectivelydisengage, or otherwise communicate with components of the vehicleaccording to various modes of operation. As shown in FIG. 3, controller210 is coupled to engine 20. In one embodiment, controller 210 isconfigured to selectively engage engine 20 (e.g., interface with athrottle of, etc.) such that an output of engine 20 spins at a targetrate. Controller 210 is coupled to first electromagnetic device 40 andsecond electromagnetic device 50, according to an exemplary embodiment,and may send and receive signals therewith. By way of example,controller 210 may send command signals relating to at least one of atarget rotational speed and a target rotation direction for firstelectromagnetic device 40 and second electromagnetic device 50. As shownin FIG. 3, first electromagnetic device 40 and second electromagneticdevice 50 are electrically coupled. By way of example, power generatedby first electromagnetic device 40 may be utilized by secondelectromagnetic device 50 (e.g., to provide an output torque as a motor,etc.), or power generated by second electromagnetic device 50 may beutilized by first electromagnetic device 40 (e.g., to provide an outputtorque as a motor, etc.).

According to the exemplary embodiment shown in FIG. 3, control system200 includes a user interface 220 that is coupled to controller 210. Inone embodiment, user interface 220 includes a display and an operatorinput. The display may be configured to display a graphical userinterface, an image, an icon, or still other information. In oneembodiment, the display includes a graphical user interface configuredto provide general information about the vehicle (e.g., vehicle speed,fuel level, warning lights, etc.). The graphical user interface may alsobe configured to display a current mode of operation, various potentialmodes of operation, or still other information relating to transmission30 or drive system 100. By way of example, the graphical user interfacemay be configured to provide specific information regarding theoperation of drive system 100 (e.g., whether power split coupled clutch130, input coupled clutch 140, output coupled clutch 150, and outputbrake 170 are engaged or disengaged, a fault condition where at leastone of power split coupled clutch 130, input coupled clutch 140, outputcoupled clutch 150, and output brake 170 fail to engage or disengage inresponse to a command signal, etc.).

The operator input may be used by an operator to provide commands to atleast one of engine 20, transmission 30, first electromagnetic device40, second electromagnetic device 50, and drive system 100 or stillanother component of the vehicle. The operator input may include one ormore buttons, knobs, touchscreens, switches, levers, or handles. In oneembodiment, an operator may press a button to change the mode ofoperation for at least one of transmission 30, and drive system 100, andthe vehicle. The operator may be able to manually control some or allaspects of the operation of transmission 30 using the display and theoperator input. In should be understood that any type of display orinput controls may be implemented with the systems and methods describedherein.

Controller 210 may be implemented as a general-purpose processor, anapplication specific integrated circuit (ASIC), one or more fieldprogrammable gate arrays (FPGAs), a digital-signal-processor (DSP),circuits containing one or more processing components, circuitry forsupporting a microprocessor, a group of processing components, or othersuitable electronic processing components. According to the exemplaryembodiment shown in FIG. 3, controller 210 includes a processing circuit212 and a memory 214. Processing circuit 212 may include an ASIC, one ormore FPGAs, a DSP, circuits containing one or more processingcomponents, circuitry for supporting a microprocessor, a group ofprocessing components, or other suitable electronic processingcomponents. In some embodiments, processing circuit 212 is configured toexecute computer code stored in memory 214 to facilitate the activitiesdescribed herein. Memory 214 may be any volatile or non-volatilecomputer-readable storage medium capable of storing data or computercode relating to the activities described herein. According to anexemplary embodiment, memory 214 includes computer code modules (e.g.,executable code, object code, source code, script code, machine code,etc.) configured for execution by processing circuit 212. Memory 214includes various actuation profiles corresponding to modes of operation(e.g., for transmission 30, for drive system 100, for a vehicle, etc.),according to an exemplary embodiment. In some embodiments, controller210 may represent a collection of processing devices (e.g., servers,data centers, etc.). In such cases, processing circuit 212 representsthe collective processors of the devices, and memory 214 represents thecollective storage devices of the devices.

Referring next to the exemplary embodiments shown in FIGS. 4-10,transmission 30 is configured to operate according to a plurality ofmodes of operation. Various modes of operation for transmission 30 areidentified below in Table 1. In other embodiments, a vehicle havingtransmission 30 is configured to operate according to the various modesof operation shown in FIGS. 4-10 and identified below in Table 1.

TABLE 1 Input Power Split Output Coupled Output Coupled Mode of CoupledClutch Clutch Brake Clutch Operation 130 150 170 140 High Speed X XReverse Low Speed X X Reverse Vehicle Start X X Low Range X X Mid RangeX X Shift X X X High Range X X

As shown in Table 1, an “X” represents a component of drive system 100(e.g., output brake 170, power split coupled clutch 130, etc.) that isengaged or closed during the respective modes of operation. In oneembodiment, all of the components in Table 1 are disengaged toselectively reconfigure transmission 30 in a neutral mode.

As shown in FIG. 4, transmission 30 is selectively reconfigured into anactive neutral startup mode of operation (e.g., a vehicle start mode ofoperation, an active neutral mode of operation, etc.). Controller 210may selectively configure transmission 30 into the active neutralstartup mode of operation in response to a vehicle start request and/oran engine start request. Controller 210 may selectively configuretransmission 30 into the active neutral startup mode of operation from apassive neutral mode of operation (e.g., a mode whereby engine 20 isrunning but does not provide an output torque to tires 62 and/or tires72, etc.). In one embodiment, controller 210 first selectivelyconfigures transmission 30 into the passive neutral mode of operation(e.g., by starting engine 20, etc.) and thereafter selectively configuretransmission 30 into the active neutral startup mode of operation inresponse to the vehicle start request and/or the engine start request.Transmission 30 may be reconfigured into the passive neutral mode ofoperation at various times during the operation of the vehicle (e.g.,when entering a park mode of operation from a driving mode of operation,in order to tow the vehicle, etc.).

In one embodiment, engine 20 includes a traditional starting mechanism(e.g., a starter motor, etc.) configured to start engine 20 (e.g., inresponse to a vehicle start request, in response to an engine startrequest, etc.). The vehicle start request and/or the engine startrequest may include a directive to turn the engine “on” from an “off”state. The vehicle may include at least one of a pushbutton, a graphicaluser interface, an ignition, and another device with which a userinteracts to provide or trigger the vehicle start request and/or theengine start request. In other embodiments, the vehicle start requestand/or the engine start request is generated by an autonomous controlsystem configured to command the vehicle or engine to turn “on” from an“off” state. Controller 210 may provide a signal to first start engine20 and thereafter selectively configure transmission 30 into the activeneutral startup mode of operation in response to a vehicle start requestand/or an engine start request.

In the active neutral startup mode of operation, engine 20 may provide arotational mechanical energy input to at least one of firstelectromagnetic device 40 and second electromagnetic device 50. In oneembodiment, first electromagnetic device 40 is coupled to secondelectromagnetic device 50 with a bus. The bus may include an electricalconnection, and a voltage produced by first electromagnetic device 40 inresponse to the rotational input from engine 20 may be applied to thebus. First electromagnetic device 40 may produce a voltage that isapplied to the bus when transmission 30 is configured in the activeneutral startup mode of operation. In another embodiment, the at leastone of first electromagnetic device 40 and second electromagnetic device50 may provide a startup power in response to a rotational input fromengine 20.

In the active neutral startup mode of operation, engine 20 powers atleast one of the first electromagnetic device 40 and secondelectromagnetic device 50, which is brought up to a threshold level(e.g., a threshold speed, a threshold speed for a target period of time,performance that provides a threshold power generation, performance thatprovides a threshold power generation for a target period of time,performance that provides a threshold startup power, etc.). Thethreshold level may relate to a requisite DC bus voltage needed toactivate at least one of first electromagnetic device 40 and secondelectromagnetic device 50. The power electronics of control system 200that control the motor-to-motor functions may be brought online duringthe active neutral startup mode. In one embodiment, controller 210activates first electromagnetic device 40 and/or second electromagneticdevice 50 within and/or to a desired state in response to firstelectromagnetic device 40 operating at the threshold level. In anotherembodiment, controller 210 disengages at least one of input coupledclutch 140 and output brake 170 in response to first electromagneticdevice 40 operating at the threshold level.

According to an exemplary embodiment, transmission 30 is selectivelyreconfigured into the active neutral startup mode during an initialstart of engine 20 (e.g., when engine is turned “on” from an “off”state, etc.). The active neutral startup mode may differ from otherneutral modes of operation associated with the vehicle (e.g., innon-startup conditions, etc.), where first electromagnetic device 40 andsecond electromagnetic device 50 are already actuatable into a desiredstate and/or otherwise online.

In an alternative embodiment, at least one of first electromagneticdevice 40 and second electromagnetic device 50 include and/or arecoupled an energy storage device (e.g., a capacitor, a battery, etc.)configured to store energy (e.g., electrical energy, chemical energy,etc.) associated with drive system 100. In one embodiment, rotation offirst electromagnetic device 40 rotates connecting shaft 36 to startengine 20. By way of example, first electromagnetic device 40 may beconfigured to use the stored energy to start engine 20 by providing arotational mechanical energy input (e.g., a torque, etc.) to engine 20via connecting shaft 36. In another embodiment, rotation of secondelectromagnetic device 50 rotates connecting shaft 36 (e.g., where inputcoupled clutch 140 is engaged, etc.) to start engine 20. By way ofexample, second electromagnetic device 50 may be configured to use thestored energy to start engine 20 by providing a rotational mechanicalenergy input (e.g., a torque, etc.) to engine 20 through the engagementof input coupled clutch 140 with connecting shaft 36. Such an activeneutral startup mode may be used to start engine 20, establish arequisite DC bus voltage, and/or otherwise export power without relyingon controller 210 to engage first electromagnetic device 40 and/orsecond electromagnetic device 50.

As shown in FIG. 4 and Table 1, input coupled clutch 140 and outputbrake 170 are engaged when transmission 30 is configured in the activeneutral startup mode. As shown in FIG. 4, input coupled clutch 140directly couples second electromagnetic device 50 to connecting shaft 36and engine 20. Output brake 170 rotationally fixes ring gear 124. Whenengine 20 provides a rotational mechanical energy input to transmission30, connecting shaft 36 drives both power split planetary 110 (e.g.,directly, etc.) and output planetary 120 (e.g., through secondelectromagnetic device 50, etc.). According to the exemplary embodimentshown in FIG. 4, an energy flow path for the active neutral startup modeincludes: engine 20 providing a rotational mechanical energy input toconnecting shaft 36; connecting shaft 36 conveying the rotationalmechanical energy to ring gear 114 and second electromagnetic device 50(e.g., through input coupled clutch 140, etc.); and secondelectromagnetic device 50 transferring the rotational mechanical energyinput to sun gear 122. With the rotation of ring gear 124 selectivelyfixed by output brake 170, the rotation of sun gear 122 rotates theplurality planetary gears 126 about central axes thereof, as well asabout sun gear 122. The rotation of the plurality planetary gears 126about the sun gear 122 drives carrier 128, and carrier 128 therebydrives carrier 118.

Referring still to FIG. 4, ring gear 114 is driven directly byconnecting shaft 36. As shown in FIG. 4, carrier 118 is indirectlydriven by connecting shaft 36 (e.g., by output planetary 120 when inputcoupled clutch 140 is engaged, etc.). The rotation of ring gear 114 andcarrier 118 rotates the plurality of planetary gears 116 about centralaxes thereof such that sun gear 112 rotates. The rotation of sun gear112 drives first electromagnetic device 40. In one embodiment, firstelectromagnetic device 40 thereby provides a startup power in responseto a rotational input from engine 20. The rotation of sun gear 112 mayfacilitate first electromagnetic device 40 establishing a requisiteoperating condition (e.g., a requisite DC bus voltage, etc.) forcontrolling first electromagnetic device 40 and/or secondelectromagnetic device 50 in one or more desired states. In someembodiments, second electromagnetic device 50 is brought up to thethreshold individually or jointly with first electromagnetic device 40to establish the requisite DC bus voltage and control firstelectromagnetic device 40 and/or second electromagnetic device 50 in adesired state.

An alternative energy flow path in the active neutral startup mode inwhich drive system 100 includes: an energy storage device may includefirst electromagnetic device 40 providing a rotational mechanical energyinput to sun gear 112 that is received by the plurality of planetarygears 116; the plurality of planetary gears 116 conveying the rotationalmechanical energy to ring gear 114; and ring gear 114 transferring therotational mechanical energy to connecting shaft 36 such that therotational mechanical energy provided by first electromagnetic device 40starts engine 20.

According to the exemplary embodiment shown in FIG. 4, engaging inputcoupled clutch 140 rotates second electromagnetic device 50 at therotational speed of connecting shaft 36. Connecting shaft 36 may rotateat the same speed as engine 20 such that engine 20 and secondelectromagnetic device 50 operate at a 1:1 speed ratio. According to theexemplary embodiment shown in FIG. 4, engaging input coupled clutch 140and output brake 170 rotates carrier 118 (e.g., through output planetary120, etc.) while ring gear 114 rotates with connecting shaft 36.Engaging input coupled clutch 140 and output brake 170 may drive firstelectromagnetic device 40 at a rotational speed that is related to therotational speed of carrier 118 and the rotational speed of ring gear114. In one embodiment, the active neutral startup mode locks firstelectromagnetic device 40 and second electromagnetic device 50 in afixed speed ratio with engine 20 (e.g., 1:1 between secondelectromagnetic device 50 and engine 20; 1.06:1 between firstelectromagnetic device 40 and engine 20, etc.).

Referring still to FIG. 4, transmission 30 isolates engine 20 fromoutput shaft 32 during the active neutral startup mode (e.g., powersplit coupled clutch 130 and output coupled clutch 150 may bedisengaged, etc.). Such isolation may reduce (e.g., substantiallyeliminate, etc.) a forward lurch potential traditionally associated withstarting the vehicle (e.g., transmission 30 does not provide an outputtorque to tires 62 and/or tires 72 when in the active neutral startupmode, etc.).

In some embodiments, input coupled clutch 140 and output brake 170remain engaged after first electromagnetic device 40 and/or secondelectromagnetic device 50 are activated into one or more desiredoperating states. With transmission 30 in the active neutral startupmode and first electromagnetic device 40 and/or second electromagneticdevice 50 activated into one or more desired operating states, drivesystem 100 may generate electrical power. By way of example, rotation ofconnecting shaft 36 may rotate first electromagnetic device 40 and/orsecond electromagnetic device 50 to generate electrical power. In oneembodiment, the electrical power is stored for future use. In anotherembodiment, the electrical power is used to actively power devicesassociated with the vehicle. In still another embodiment, the electricalpower is used to power external devices (e.g., provide export power,etc.).

In other embodiments, at least one of input coupled clutch 140 andoutput brake 170 are disengaged in response to the generated startuppower, the speed of first electromagnetic device 40 and/or secondelectromagnetic device 50, the generated voltage, and/or the generatedvoltage and generation time exceeding a threshold level. Suchdisengagement may prepare transmission 30 to be selectively reconfiguredinto a drive mode (e.g., low range, mid range, high range, etc.). By wayof example, input coupled clutch 140 may be disengaged in response tofirst electromagnetic device 40 and second electromagnetic device 50being activated and controlled (e.g., by controller 210, etc.). Onlypower split coupled clutch 130 may need to be engaged to selectivelyreconfigure transmission 30 into the mid range mode, thereby providing asimple and efficient process by which the vehicle may be shifted into adrive mode and driven. In one embodiment, activating one or more of theelectromagnetic devices includes controlling second electromagneticdevice 50 in a motoring mode where second electromagnetic device 50provides an input torque to transmission 30 and is commanded to operateat a target speed. Such a speed may be based on the current vehiclespeed (e.g., zero if the vehicle is not moving on flat ground, non-zeroif the vehicle is rolling up or down a slope at startup, etc.).Commanding the operation of second electromagnetic device 50 may preparetransmission 30 for a shift from the active neutral startup mode ofoperation (i.e., a selective reconfiguration, etc.) to another drivingmode of operation (e.g., a mid range mode of operation, etc.). Suchpreparation may decrease an inertial jerk on output shaft 32 during theshift.

As shown in FIG. 5, transmission 30 is selectively reconfigured into alow range mode of operation such that transmission 30 allows for a lowoutput speed operation with a high output torque. The low range modeincreases a vehicle's gradability (e.g., facilitates the vehiclemaintaining speed on a grade, etc.). In one embodiment, engine 20provides a rotational mechanical energy input to transmission 30 suchthat first electromagnetic device 40 generates electrical power andsecond electromagnetic device 50 uses the generated electrical power toprovide a rotational mechanical energy input to transmission 30. Assuch, engine 20 and second electromagnetic device 50 provide arotational mechanical energy input to drive at least one of tires 62 andtires 72. In an alternative embodiment, first electromagnetic device 40operates as a motor and second electromagnetic device 50 operates as agenerator when transmission 30 is configured in the low range mode.

As shown in FIG. 5 and Table 1, power split coupled clutch 130 andoutput coupled clutch 150 are engaged when transmission 30 is configuredin the low range mode. As shown in FIG. 5, power split coupled clutch130 and output coupled clutch 150 couple gear set 180 and gear set 190to output shaft 32, respectively. Accordingly, when engine 20 provides arotational mechanical energy input to transmission 30, both power splitplanetary 110 and output planetary 120 drive output shaft 32 via gearset 180 and gear set 190, respectively. According to the exemplaryembodiment shown in FIG. 5, an energy flow path for the low rangeincludes: engine 20 providing a rotational mechanical energy input toconnecting shaft 36; connecting shaft 36 conveying the rotationalmechanical energy to ring gear 114; ring gear 114 causing the pluralityof planetary gears 116 to rotate about central axes thereof, as well asabout sun gear 112 such that both carrier 118 and sun gear 112 rotate;and the rotation of sun gear 112 driving first electromagnetic device 40such that it operates as a generator (e.g., generates electrical energy,etc.).

Referring still to FIG. 5, the rotation of carrier 118 drives bothcarrier 128 and gear set 180. Carrier 128 drives the plurality ofplanetary gears 126 to rotate about sun gear 122 and about central axesthereof. In one embodiment, second electromagnetic device 50 receiveselectrical energy generated by first electromagnetic device 40.Accordingly, second electromagnetic device 50 operates as a motor,providing a rotational mechanical energy input to sun gear 122. The sungear 122 conveys the rotational mechanical energy to the plurality ofplanetary gears 126 such that each further rotates about the centralaxis thereof. The plurality of planetary gears 126 drive ring gear 124,and the rotation of ring gear 124 drives gear set 190. According to theexemplary embodiment shown in FIG. 6, gear set 180 and gear set 190transfer a torque to and from output shaft 32 with power split coupledclutch 130 and output coupled clutch 150 engaged. As such, engine 20 andsecond electromagnetic device 50 move a vehicle at a low speed with ahigh output torque.

As shown in FIG. 6, transmission 30 is selectively reconfigured into amid range mode of operation such that transmission 30 allows for a midrange output speed operation. The mid range mode may improve low outputspeed torque and high output speed power. In one embodiment, engine 20provides a rotational mechanical energy input such that firstelectromagnetic device 40 generates electrical power, and secondelectromagnetic device 50 uses the generated electrical power to providea rotational mechanical energy input to transmission 30. Secondelectromagnetic device 50 thereby provides a rotational mechanicalenergy input to drive at least one of tires 62 and tires 72. In analternative embodiment, second electromagnetic device 50 operates as agenerator while first electromagnetic device 40 operates as a motor whentransmission 30 is configured in the mid range mode. In still anotheralternative embodiment, both first electromagnetic device 40 and secondelectromagnetic device 50 operate as a generator in the mid range mode.

As shown in FIG. 6 and Table 1, power split coupled clutch 130 andoutput brake 170 are engaged when transmission 30 is configured in themid range mode. As shown in FIG. 6, output brake 170 inhibits therotation of gear set 190 (e.g., gear 192, gear 194, gear 196, etc.).Output brake 170 thereby rotationally fixes ring gear 124. In oneembodiment, engaging output brake 170 substantially eliminates a powerdip between output and input modes of transmission 30. According to theexemplary embodiment shown in FIG. 6, an energy flow path for the midrange mode includes: engine 20 providing a rotational mechanical energyinput to connecting shaft 36 that is conveyed to ring gear 114; ringgear 114 driving the plurality of planetary gears 116 to rotate aboutcentral axes thereof, as well as about sun gear 112 such that bothcarrier 118 and sun gear 112 rotate; and the rotation of carrier 118driving carrier 128, which rotates the plurality planetary gears 126about central axes thereof, as well as about sun gear 122.

With ring gear 124 fixed by output brake 170, second electromagneticdevice 50 may operate as a motor. In one embodiment, secondelectromagnetic device 50 receives electrical energy generated by firstelectromagnetic device 40. First electromagnetic device 40 operates as agenerator, removing a rotational mechanical energy from sun gear 112.The sun gear 122 conveys the rotational mechanical torque to theplurality of planetary gears 126 such that each further rotates aboutsun gear 122 (e.g., at an increased rotational speed, etc.). Therotation of the plurality of planetary gears 126 (e.g., effected by sungear 122, etc.) drives carrier 128 and thereby gear set 180. As shown inFIG. 6, power split coupled clutch 130 couples gear set 180 to outputshaft 32 such that the rotational mechanical energy of gear set 180,received from second electromagnetic device 50, drives output shaft 32at a mid range output speed and may thereby drive a vehicle at a midrange output speed.

As shown in FIG. 7, transmission 30 is selectively reconfigured into ahigh range mode of operation such that transmission 30 allows for a highoutput speed operation. In one embodiment, engine 20 provides arotational mechanical energy input such that second electromagneticdevice 50 generates electrical power while first electromagnetic device40 uses the generated electrical power to provide a rotationalmechanical energy input to transmission 30. As such, engine 20 and firstelectromagnetic device 40 provide a rotational mechanical energy inputto drive at least one of tires 62 and tires 72. In an alternativeembodiment, first electromagnetic device 40 operates as a generator andsecond electromagnetic device 50 operates as a motor when transmission30 is configured in the high range mode.

As shown in FIG. 7 and Table 1, power split coupled clutch 130 and inputcoupled clutch 140 are engaged when transmission 30 is configured in thehigh range mode. As shown in FIG. 7, the engagement of input coupledclutch 140 with connecting shaft 36 rotationally couples engine 20 andsecond electromagnetic device 50. By way of example, engine 20 mayprovide a rotational mechanical energy input to connecting shaft 36 suchthat second electromagnetic device 50 generates electrical energy. Inone embodiment, first electromagnetic device 40 receives the electricalenergy generated by second electromagnetic device 50. Firstelectromagnetic device 40 operates as a motor, providing a rotationalmechanical energy input to sun gear 112 that drives the plurality ofplanetary gears 116 and carrier 118.

Referring still to FIG. 7, power from engine 20 is transferred to ringgear 114 and the plurality of planetary gears 116. The plurality ofplanetary gears 116 are driven by both engine 20 (e.g., via ring gear114, etc.) and first electromagnetic device 40 (e.g., via sun gear 112,etc.). Carrier 118 rotates, which drives gear set 180. As shown in FIG.7, power split coupled clutch 130 couples gear set 180 to output shaft32 such that the rotational mechanical energy provided by engine 20 andfirst electromagnetic device 40 drives a vehicle at a high range speed.

As shown in FIG. 8, transmission 30 is selectively reconfigured into anintermediate shift mode of operation that facilitates transitioningtransmission 30 (i.e., shifting, changing modes, etc.) between the midrange mode of operation and the high range mode of operation. Accordingto the embodiment shown in FIG. 8, input coupled clutch 140, power splitcoupled clutch 130, and output brake 170 are engaged when transmission30 is selectively reconfigured into the intermediate shift mode ofoperation. According to an exemplary embodiment, the intermediate shiftmode provides a smooth and robust shifting strategy that functionsreliably even in a wide variety of operating conditions, when usingvarious types of oil for the components of transmission 30, and whenexperiencing valve nonlinearities that may be present in one or morevalves of transmission 30. The intermediate shift mode may provide azero inertia shift through and across two or more overlapping ranges(e.g., the mid range and the high range, etc.). According to theexemplary embodiment shown in FIGS. 6-8, the intermediate shift modeeliminates the need to simultaneously disengage output brake 170 andengage input coupled clutch 140 to shift from the mid range mode to thehigh range mode, or vice versa. The intermediate shift mode reducesjerking sensations associated with simultaneously disengaging outputbrake 170 and engaging input coupled clutch 140 to shift from mid rangeto high range, providing a smoother ride.

During operation, the intermediate shift mode may be used to shift frommid range mode to high range mode or from high range mode to mid rangemode. In one embodiment, transmission 30 is configured in the mid rangemode of operation with power split coupled clutch 130 and output brake170 engaged and configured in the high range mode of operation withpower split coupled clutch 130 and input coupled clutch 140 engaged.Transmission 30 may be selectively reconfigured into the intermediateshift mode in response to the difference between a rotational speed ofsecond electromagnetic device 50 and a rotational speed of connectingshaft 36 and/or engine 20 falling below or equaling a threshold level(e.g., approximately zero, five revolutions per minute, fiftyrevolutions per minute, etc.). Transmission 30 may enter theintermediate shift mode when the rotational speed of secondelectromagnetic device 50 substantially corresponds with (e.g., matches,is substantially equal to, etc.) the rotational speed of connectingshaft 36 and/or engine 20. In one embodiment, transmission 30 enters theintermediate shift mode when the rotational speeds of secondelectromagnetic device 50 and connecting shaft 36 and/or engine 20 arebetween 1,600 and 1,800 revolutions per minute (RPM). By way of example,transmission 30 may enter the intermediate shift mode when therotational speeds of second electromagnetic device 50 and connectingshaft 36 and/or engine 20 are about 1,600 RPM. One or more sensors maybe positioned to monitor the rotational speed of at least one of engine20, connecting shaft 36, a portion of second electromagnetic device 50,or still another component. A controller (e.g., controller 210, etc.)may reconfigure transmission 30 into the intermediate shift mode inresponse to sensing signals provided by the one or more sensors.

Shifting into the intermediate shift mode occurs when there is limited(if any) relative movement between clutch disks of input coupled clutch140. Transmission 30 may be reconfigured into the intermediate shiftmode without compromising vehicle performance (e.g., since torque is notremoved from output shaft 32, etc.). The intermediate shift mode reduces(e.g., minimizes, etc.) heat generation and clutch wear during shifts bylimiting the relative movement between clutch disks of input coupledclutch 140 upon engagement. The intermediate shift mode may therebyincrease clutch life.

In operation, the vehicle may be accelerating in the mid range mode. Inone embodiment, second electromagnetic device 50 provides an outputtorque in the mid range mode of operation and its speed therebyincreases with the speed of the vehicle. As the speed of secondelectromagnetic device 50 continues to increase with vehicle speed,second electromagnetic device 50 may begin to operate at a rotationalspeed similar to that of connecting shaft 36 and/or engine 20.Controller 210 may engage input coupled clutch 140 to selectivelyreconfigure transmission 30 into the intermediate shift mode from themid range mode. The vehicle may alternatively be decelerating in thehigh range mode. In one embodiment, first electromagnetic device 40operates as a motor in the high range mode of operation with its speedrelated to that of connecting shaft 36, engine 20, and/or the speed ofthe vehicle. The speed of the vehicle and/or the speed of firstelectromagnetic device 40 may decrease to a speed designated for midrange mode. Controller 210 may engage output brake 170 to selectivelyreconfigure transmission 30 into the intermediate shift mode from thehigh range mode.

As shown in FIGS. 6-8, power split coupled clutch 130 is engaged (i.e.,is not disengaged, is not open, transfers torque, etc.) in each of themid range mode, the intermediate shift mode, and the high mode.Transmission 30 having power split coupled clutch 130 engaged in each ofthese modes facilitates the continuous transfer of power from engine 20to output shaft 32 during the shift from mid range mode to high rangemode. According to an exemplary embodiment, engine 20 is also coupled tooutput shaft 32 via power split coupled clutch 130 at a fixed ratioduring the intermediate shift mode. Maintaining a power path to outputshaft 32 during the shift reduces (e.g., eliminates, etc.) jerkingassociated with shifting traditional transmission systems. In theintermediate shift mode, an acceleration of engine 20 causes anacceleration of the vehicle, and a deceleration of engine 20 causes adeceleration of the vehicle. Powering the vehicle with engine 20 duringthe shift event increases the overall efficiency of drive system 100 byreducing the electrical power path during the shift event.

Transmission 30 may be configured in the intermediate shift mode for anextended period of time and/or while the while the vehicle traverses anextended distance. Controller 210 may selectively reconfiguretransmission 30 out of the intermediate shift mode (e.g., into the midrange mode of operation, into the high range mode of operation, etc.)automatically in response to at least one of an elapsed shift time(e.g., a time that has elapsed while in the intermediate shift mode,etc.), a traveled shift distance (e.g., a distance the vehicle hastraveled while in the intermediate shift mode, etc.), a change in enginespeed, and a request, among other conditions.

In one embodiment, controller 210 transitions transmission 30 out of theintermediate shift mode in response to an indication that the shift hassatisfied at least one of a time-based and a distance-based condition.By way of one example, controller 210 may transition transmission 30 outof the intermediate shift mode in response to an indication thattransmission 30 has been in the intermediate shift mode for longer thana predetermined period of time. By way of another example, controller210 may transition transmission 30 out of the intermediate shift mode inresponse to an indication that the vehicle has traversed more than athreshold distance.

In another embodiment, controller 210 transitions transmission 30 out ofthe intermediate shift mode in response to a change in engine speed.Controller 210 may selectively reconfigure transmission 30 into the highrange mode from the intermediate shift mode (e.g., by disengaging outputbrake 170, etc.) in response to an increase in engine speed (e.g., inresponse to the speed of engine 20 exceeding a threshold speed, etc.).By way of example, the vehicle may encounter a downhill slope, causingthe engine speed to increase, and thereby prompting a shift into thehigh range mode of operation. By way of another example, the enginespeed may increase based on a command (e.g., provided by an operatorusing an accelerator pedal or another input device, provided by acontroller as part of an autonomous operation of the vehicle, etc.) thatprompts the engine speed to increase.

Controller 210 may selectively reconfigure transmission 30 into the midrange mode from the intermediate shift mode (e.g., by disengaging inputcoupled clutch 140, etc.) in response to a decrease in engine speed(e.g., in response to the speed of engine 20 falling below a thresholdspeed, etc.). By way of example, the vehicle may encounter an uphillslope, causing the engine speed to decrease, and thereby prompting ashift into the mid range mode of operation. By way of another example,the engine speed may decrease based on a command (e.g., provided by anoperator using a brake pedal or another input device, provided by anoperator releasing an accelerator pedal or another input device,provided by a controller as part of an autonomous operation of thevehicle, etc.) that prompts the engine speed to decrease.

In still another embodiment, controller 210 transitions transmission 30out of the intermediate shift mode in response to a request. By way ofexample, the request may come from an operator (e.g., provided by way ofa user interface, etc.) and indicate the operator's command to entereither the mid range mode of operation or the high range mode ofoperation. The request may also be provided by a controller as part ofan autonomous operation of the vehicle. Such requests may be provided inorder to reenter a mode of operation whereby the vehicle operates moreefficiently. Such requests may prompt transmission 30 to complete theshift from the mid range mode of operation to the high range mode ofoperation, complete the shift from the high range mode of operation tothe mid range mode of operation, toggle back into the mid range mode ofoperation from the intermediate shift mode, and/or toggle back into thehigh range mode of operation from the intermediate shift mode.

In some embodiments, transmission 30 is selectively reconfigured intothe intermediate shift mode from one of the mid range mode and the highrange mode, and then is selectively reconfigured back into the previousmode (e.g., mid range mode to intermediate shift mode to mid range mode,etc.). By way of example, transmission 30 may be reconfigured into theintermediate shift mode from the mid range mode in response to secondelectromagnetic device 50 and engine 20 having a speed differentialbelow a threshold level. An operator may keep engine 20 operating atsubstantially the same speed for a period of time, driving output shaft32 with engine 20, and then release the accelerator pedal wherebytransmission 30 may be returned to the mid range mode. In oneembodiment, first electromagnetic device 40 generates electricity in theintermediate shift mode. Second electromagnetic device 50 may provide anoutput torque to output shaft 32 in the intermediate shift mode. Inanother embodiment, second electromagnetic device 50 generateselectricity in the intermediate shift mode. First electromagnetic device40 may provide an output torque to output shaft 32 in the intermediateshift mode. In still another embodiment, neither or both of firstelectromagnetic device 40 and second electromagnetic device 50 generateelectrical power and/or provide output torque in the intermediate shiftmode.

As shown in FIG. 9, transmission 30 is selectively reconfigured into alow speed reverse mode of operation. In one embodiment, engine 20provides a rotational mechanical energy input to transmission 30 suchthat first electromagnetic device 40 generates electrical power andsecond electromagnetic device 50 uses the generated electrical power toprovide a rotational mechanical energy input to transmission 30. Assuch, engine 20 and second electromagnetic device 50 provide arotational mechanical energy input to drive at least one of tires 62 andtires 72 in a reverse direction (e.g., backwards, etc.). In analternative embodiment, first electromagnetic device 40 operates as amotor and second electromagnetic device 50 operates as a generator whentransmission 30 is configured in the low speed reverse mode.

As shown in FIG. 9 and Table 1, power split coupled clutch 130 andoutput coupled clutch 150 are engaged when transmission 30 is configuredin the low speed reverse mode. As shown in FIG. 9, the low speed reversemode is substantially similar to the low range mode of FIG. 5 in thatpower split coupled clutch 130 and output coupled clutch 150 couple bothgear set 180 and gear set 190 to output shaft 32. In the low speedreverse mode, second electromagnetic device 50 may provide a rotationalmechanical energy input to transmission 30 in an opposite direction ascompared to the low range mode of FIG. 5.

As shown in FIG. 10, transmission 30 is selectively reconfigured into ahigh speed reverse mode of operation such that transmission 30 allowsfor a high reverse output speed operation. In one embodiment, engine 20provides a rotational mechanical energy input such that firstelectromagnetic device 40 generates electrical power, and secondelectromagnetic device 50 uses the generated electrical power to providea rotational mechanical energy input to transmission 30. As such, secondelectromagnetic device 50 provides a rotational mechanical energy inputto drive at least one of tires 62 and tires 72. In an alternativeembodiment, second electromagnetic device 50 operates as a generator andfirst electromagnetic device 40 operates as a motor when transmission 30is configured in the high speed reverse mode. In still anotheralternative embodiment, both first electromagnetic device 40 and secondelectromagnetic device 50 operate as a generator in the high speedreverse mode.

As shown in FIG. 10 and Table 1, power split coupled clutch 130 andoutput brake 170 are engaged when transmission 30 is configured in thehigh speed reverse mode. As shown in FIG. 10, output brake 170 inhibitsthe rotation of gear set 190 (e.g., gear 192, gear 194, gear 196, etc.).Output brake 170 thereby rotationally fixes ring gear 124. According tothe exemplary embodiment shown in FIG. 10, an energy flow path for thehigh speed reverse mode includes: engine 20 providing a rotationalmechanical energy input to connecting shaft 36 that is conveyed to ringgear 114; and ring gear 114 driving the plurality of planetary gears 116to rotate about central axes thereof, as well as about sun gear 112 suchthat both carrier 118 and sun gear 112 rotate.

Referring still to FIG. 10, the rotation of carrier 118 drives carrier128, which rotates the plurality planetary gears 126 about central axesthereof, as well as about sun gear 122. With ring gear 124 fixed byoutput brake 170, second electromagnetic device 50 may operate as amotor. In one embodiment, second electromagnetic device 50 receiveselectrical energy generated by first electromagnetic device 40.Accordingly, first electromagnetic device 40 operates as a generator,removing a rotational mechanical energy from sun gear 112. The sun gear122 conveys the rotational mechanical torque to the plurality ofplanetary gears 126 such that each further rotates about sun gear 122(e.g., at an increased rotational speed, etc.). The rotation of theplurality of planetary gears 126 (e.g., effected by sun gear 122, etc.)drives carrier 128 and thereby gear set 180. As shown in FIG. 10, powersplit coupled clutch 130 couples gear set 180 to output shaft 32 suchthat the rotational mechanical energy of gear set 180, received fromsecond electromagnetic device 50, drives output shaft 32 at a highreverse output speed and may thereby drive a vehicle at a high reverseoutput speed.

According to an alternative embodiment, engine 20 does not provide arotational mechanical energy input to drive a vehicle. By way ofexample, first electromagnetic device 40, second electromagnetic device50, and/or another device may store energy during the above mentionedmodes of operation. When sufficient energy is stored (e.g., above athreshold level, etc.), at least one of first electromagnetic device 40and second electromagnetic device 50 may provide a rotational mechanicalenergy input to transmission 30 such that the vehicle is driven withoutan input from engine 20 (e.g., an electric mode, etc.).

Although this description may discuss a specific order of method steps,the order of the steps may differ from what is outlined. Also two ormore steps may be performed concurrently or with partial concurrence.Such variation will depend on the software and hardware systems chosenand on designer choice. All such variations are within the scope of thedisclosure. Likewise, software implementations could be accomplishedwith standard programming techniques with rule-based logic and otherlogic to accomplish the various connection steps, processing steps,comparison steps, and decision steps. contrariwise

As utilized herein, the terms “approximately”, “about”, “substantially”,and similar terms are intended to have a broad meaning in harmony withthe common and accepted usage by those of ordinary skill in the art towhich the subject matter of this disclosure pertains. It should beunderstood by those of skill in the art who review this disclosure thatthese terms are intended to allow a description of certain featuresdescribed and claimed without restricting the scope of these features tothe precise numerical ranges provided. Accordingly, these terms shouldbe interpreted as indicating that insubstantial or inconsequentialmodifications or alterations of the subject matter described and claimedare considered to be within the scope of the invention as recited in theappended claims.

It should be noted that the term “exemplary” as used herein to describevarious embodiments is intended to indicate that such embodiments arepossible examples, representations, and/or illustrations of possibleembodiments (and such term is not intended to connote that suchembodiments are necessarily extraordinary or superlative examples).

The terms “coupled,” “connected,” and the like, as used herein, mean thejoining of two members directly or indirectly to one another. Suchjoining may be stationary (e.g., permanent, etc.) or moveable (e.g.,removable, releasable, etc.). Such joining may be achieved with the twomembers or the two members and any additional intermediate members beingintegrally formed as a single unitary body with one another or with thetwo members or the two members and any additional intermediate membersbeing attached to one another.

References herein to the positions of elements (e.g., “top,” “bottom,”“above,” “below,” “between,” etc.) are merely used to describe theorientation of various elements in the figures. It should be noted thatthe orientation of various elements may differ according to otherexemplary embodiments, and that such variations are intended to beencompassed by the present disclosure.

It is important to note that the construction and arrangement of theelectromechanical variable transmission as shown in the exemplaryembodiments is illustrative only. Although only a few embodiments of thepresent disclosure have been described in detail, those skilled in theart who review this disclosure will readily appreciate that manymodifications are possible (e.g., variations in sizes, dimensions,structures, shapes and proportions of the various elements, values ofparameters, mounting arrangements, use of materials, colors,orientations, etc.) without materially departing from the novelteachings and advantages of the subject matter recited. For example,elements shown as integrally formed may be constructed of multiple partsor elements. It should be noted that the elements and/or assemblies ofthe components described herein may be constructed from any of a widevariety of materials that provide sufficient strength or durability, inany of a wide variety of colors, textures, and combinations.Accordingly, all such modifications are intended to be included withinthe scope of the present inventions. Other substitutions, modifications,changes, and omissions may be made in the design, operating conditions,and arrangement of the preferred and other exemplary embodiments withoutdeparting from scope of the present disclosure or from the spirit of theappended claims.

What is claimed is:
 1. A vehicle, comprising: a drive axle; a multi-mode transmission including: a first gear set having a first planetary gear carrier and a second gear set having a second planetary gear carrier; a first motor/generator coupled to the first gear set; a second motor/generator coupled to the second gear set and selectively coupled to a connecting shaft; a brake positioned to selectively limit a rotational movement of a ring gear of the second gear set when engaged; a first clutch selectively rotationally coupling the first gear set and the second gear set to the drive axle when engaged; and a second clutch selectively rotationally coupling the second motor/generator to the connecting shaft when engaged; and a controller coupled to the multi-mode transmission and configured to engage the second clutch, the brake, and the first clutch to selectively reconfigure the multi-mode transmission to an intermediate shift mode of operation.
 2. The vehicle of claim 1, wherein the controller is configured to selectively transition the multi-mode transmission into the intermediate shift mode of operation in response to the second motor/generator having a rotational speed that is substantially equal to a rotational speed of the connecting shaft.
 3. The vehicle of claim 1, wherein the controller is configured to selectively transition the multi-mode transmission into the intermediate shift mode of operation in response to the difference between a rotational speed of the second motor/generator and a rotational speed of the connecting shaft falling below a threshold level.
 4. The vehicle of claim 1, wherein the connecting shaft is coupled to the drive axle through a fixed ratio when the multi-mode transmission is selectively reconfigured into the intermediate shift mode of operation.
 5. The vehicle of claim 1, wherein the controller is configured to: engage the brake and the first clutch to selectively reconfigure the multi-mode transmission into a mid range mode of operation.
 6. The vehicle of claim 5, wherein the controller is configured to: disengage the brake to selectively reconfigure the multi-mode transmission into a high range mode of operation from the intermediate shift mode of operation and thereby complete a transition between the mid range mode of operation and the high range mode of operation.
 7. The vehicle of claim 1, further comprising an engine coupled to the connecting shaft and configured to provide a rotational input to the multi-mode transmission.
 8. The vehicle of claim 1, wherein the first motor/generator and the second motor/generator are each configured to receive stored energy from an energy storage device and provide a mechanical energy output such that the multi-mode transmission is configured to drive the drive axle without receiving a mechanical energy input from an engine.
 9. The vehicle of claim 1, wherein the controller is configured to automatically transition the multi-mode transmission out of the intermediate shift mode of operation in response to at least one of an elapsed shift time, a traveled shift distance, a change in a speed of the connecting shaft, and a request.
 10. The vehicle of claim 1, wherein the first planetary gear carrier and the second planetary gear carrier are rotatably coupled, and wherein the first clutch is configured to selectively rotationally couple the first planetary gear carrier and the second planetary gear carrier to the drive axle when engaged.
 11. A drive system for a vehicle, comprising: a first gear set including a first sun gear, a first ring gear, a first plurality of planetary gears coupling the first sun gear to the first ring gear, and a first carrier rotationally supporting the first plurality of planetary gears; a second gear set including a second sun gear, a second ring gear, a second plurality of planetary gears coupling the second sun gear to the second ring gear, and a second carrier rotationally supporting the second plurality of planetary gears; a first electrical machine coupled to the first gear set; a second electrical machine coupled to the second gear set; a connecting shaft coupled to the first gear set; a brake positioned to selectively limit a rotational movement of the second gear set when engaged; a first clutch selectively rotationally coupling the first carrier and the second carrier to a driveshaft output of the vehicle when engaged; and a second clutch selectively rotationally coupling the second electrical machine to the connecting shaft when engaged, wherein the drive system is selectively reconfigurable into an intermediate shift mode of operation, in which the brake, the first clutch, and the second clutch are engaged.
 12. The drive system of claim 11, wherein the drive system is transitioned from the intermediate shift mode of operation in response to at least one of an elapsed shift time, a traveled shift distance, a change in a speed of the connecting shaft, and a request.
 13. The drive system of claim 12, wherein the connecting shaft is coupled to an engine, wherein the drive system is transitioned from the intermediate shift mode of operation and into a first mode of operation by disengaging the second clutch in response to the engine falling below a first threshold speed, and wherein the drive system is transitioned from the intermediate shift mode of operation and into a second mode of operation by disengaging the brake in response to the engine exceeding a second threshold speed.
 14. The drive system of claim 11, wherein the second clutch is disengaged to transition from the intermediate shift mode of operation to a first mode of operation, and wherein the brake is disengaged to transition from the intermediate shift mode of operation to a second mode of operation.
 15. The drive system of claim 11, wherein the connecting shaft is coupled to an engine and configured to receive a rotational input from the engine.
 16. The drive system of claim 11, wherein the first electrical machine and the second electrical machine are each configured to receive stored energy from an energy storage device and provide a mechanical energy output such that the drive system is configured to drive the driveshaft output without receiving a mechanical energy input from an engine.
 17. The drive system of claim 11, wherein the drive system is transitioned into the intermediate shift mode of operation in response to the second electrical machine having a rotational speed that is substantially equal to a rotational speed of the connecting shaft.
 18. The drive system of claim 11, wherein the drive system is transitioned into the intermediate shift mode of operation in response to the difference between a rotational speed of the second electrical machine and a rotational speed of the connecting shaft falling below a threshold level.
 19. The drive system of claim 11, wherein the connecting shaft is coupled to the driveshaft output of the vehicle through a fixed ratio when the drive system is selectively reconfigured into the intermediate shift mode of operation.
 20. A method of operating a multi-mode transmission of a vehicle, the method comprising: engaging a brake and first clutch of the multi-mode transmission to configure the multi-mode transmission into a first mode of operation whereby a first electromagnetic device is coupled to a connecting shaft, the first clutch coupling a first planetary gear set and a second planetary gear set to a driveshaft output of the vehicle when engaged; engaging a second clutch of the multi-mode transmission to couple the connecting shaft and a second electromagnetic device, thereby configuring the multi-mode transmission into an intermediate shift mode; and at least one of (i) disengaging the brake to complete a reconfiguration of the multi-mode transmission into a second mode of operation and (ii) disengaging the second clutch to revert the multi-mode transmission into the first mode of operation from the intermediate shift mode. 